Contact your Laerdal rep for assistance if you don't get an answer that works or call their tech support. Are you using more than one Vital Sim at a time and are they set on different frequencies? I had trouble trying to run the SimKid and the SimBaby at the same time and found out they were on the same frequency. Is there another vital sim in nearby room that might be giving you problems? I found out I had the wrong cord to change the frequencies attached to my boxes.